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8o

POTASSIUM BROMIDE

POTASSIUM  BITARTRATE (Cream of Tartar)
KC4HB06 = 188-2

The impure salt constitutes crude tartar (sec p. 36). The pure or refined
product forms white rhombic crystals or crystalline powder and dissolves
in about 220 parts of cold water or 15 parts of boiling water, but is insoluble
in alcohol.

It may be contaminated with small proportions of calcium, lead, copper
or iron salts, or adulterated with various mineral salts (alum or other acid
salt). Its analysis includes the following :

1.  Insoluble Substances, -i gram is either treated with 220 e.e. of
water at the ordinary temperature or boiled with 18 e.e. of water.    If the
salt is pure, a clear solution should be obtained in either ease ; any insoluble,
residue left is tested especially for calcium tartrate, calcium carbonate,
gypsum, clay, etc.

2.  Nitrates, Sulphates, Chlorides............10 grams are heated to boiling

with 30 c.c. of water, cooled and filtered, the nitrate being tested with the
ordinary reagents for these radicles.

3.  Heavy  Metals,.........5  grams are  dissolved  in  ammonia,   the  liquid

being acidified with hydrocllloric acid and treated with hydrogen sulphide,
then with ammonium sulphide, etc., according to the ordinary method of
analysis-:.

4.  Calcium Tartrate (small quantities)......-I gram is treated in the. hot

with 10 c.c. of water and a. lew drops of ammonia, until solution occurs :
ammonium oxalate should give no turbidity.

5.   Quantitative Determination.......-o'5 gram is dissolved in  boiling

water (100 c.c.) and titrated with normal alkali in presence of pheuolphtha-
lein,    i c.c, N-alkali = • 0-1882 gram of pota.ssinm bitartrate.

POTASSIUM   BROMIDE
KBr •••••• i ic)

White, deliquescent crystals, highly soluble in water. It may be con-
taminated by broniates, sulphates, chlorides, iodides and carbonates. The
tests and determinations made are as follows :

1.  Sulphates,   Metals,   Alkaline Earths."  'The   i : 10   solution   is
tested with barium nitrate (sulphates), hydrogen sulphide (heavy metals),
ammonia, ammonium sulphide and ammonium oxalate.    Sodium is detected
by the flame test or by potassium pyroantimoniate.

2.  Carbonates.-—No  effervescence  should   be  obtained  with  dilute
hydrocllloric acid.    A crystal placed on red litmus paper and moistened
with a drop of water gives a blue stain if alkali carbonate is present.

3.  Bromates.—o-i gram, moistened with very dilute sulphuric acid,
should not turn yellow or emit an odour of bromine.

4.  Iodides.-—0-5 gram, dissolved in 5 c.c. of water, is treated with a
drop of ferric chloride solution or a few crystals of potassium nitrite and arric oxide, this gives the total iron (i part Fea03   0-7 part Fe).